In U.S. Pat. No. 3,718,448, which is assigned to the assignee of the present invention and which is incorporated herein by reference, a method and apparatus for coating glass filaments with heat curable elastomers and resins is shown. In this process, the filaments from the fiber forming bushing are coated with heat curable elastomers or resins, are then combined into a plurality of strands. The plurality of strands so formed are then subjected to drying. The patent states that the gathering of the filaments into a plurality of strands may be accomplished either by using the surface tension of the coating employed or by employing a mechanical separator. The drying step eliminates the moisture from the strands and, at least partially, cures the resin or elastomeric coating on the strands.
Mechanical separators have the advantage over a "natural" split (i.e., using the surface tension phenomenon) in that a precise number of filaments in each strand can be assured. This precision is not possible when surface tension alone is used to form the strands. Further, mechanical separators readily allow for changes in the number of filaments in each strand or the number of strands being formed.
While separators are very useful in producing uniform strands, they do cause some problems. When used in a direct coating process such as described in U.S. Pat. No. 3,718,448, the separators typically used are formed of a metal, such as brass, and usually take the form of a comb having a plurality of prongs. The prongs are located such that the filaments are directed between pairs of the prongs and are gathered into strands by the prongs. The separator, if used in the process of the aforementioned patent, is located slightly above a dielectric oven or some other oven which supplies heat for drying and at least partially curing the coating on the strands. This heat, of course, rises in the direction of the separator. Because the separator is typically constructed of a metal, the separator tends to absorb heat rising from the oven rapidly. Eventually, the separator will reach a temperature where excess coating material which scrapes off of the filaments as they pass through the separator remains on the separator surface and will begin to dry, cure, and thus harden. As the fragile glass filaments pass between the prongs of the separator, contact with this dried and hardened material will cause the filaments to break out, thus necessitating stoppage in which is desired to be a continuous process. To reduce strand breaks of this nature, it is necessary to shut down the operation frequently and either clean or replace the strand separator. This, too, results in down time for the system which is not desirable. Further, cleaning of the strand separator is both time consuming and difficult depending upon the nature of the hardened coating material accumulated thereon.
For these reasons, it is desirable to mechanically separate glass filaments in a direct coating forming operation into a plurality of precise strands without the coating material for the glass filaments fouling the separator used.